Meeting the Challenge of Yellow Rust in Cereal Crops - ICARDA

Of the yellow rust samples collected in 2007–2008, 11 pathotypes of
P. striiformis f.sp. tritici were identified as the most virulent, including
pathotypes 47E223, 15E191, 47E159, 71E191, 71E175, 111E155 and 111E158,
which were virulent on cultivars Vilmorin 23, Heines Kolben, Lee, Chinese 166,
Heines VII, Compair, Nord Desprez, Heines Peko, Reichersberg 42 and
Hybrid 46. Pathotype 31E158 was virulent on Moro (Yr10, YrMor), and
pathotype 47E223 on Spaldings Prolific (Yr6, YrSP). All pathotypes studied
were completely virulent (100%) on cvs Heines Kolben, Lee, Chinese 166,
Heines VII and Reichersberg 42.
Among the differentials, Spaldings Prolific had immunity to the most
isolates. Heines Kolben (Yr6) had a susceptible reaction to almost all isolates.
Cv. Moro was resistant to the majority of the isolates.
The evaluation of field response to yellow rust in commercial cultivars and
advanced lines of wheat showed that during the epidemic of 2009, most high
yielding widely grown cultivars, such as Steklovidnaya 24, Naz, Progress and
Zhetisu, had severe stripe rust. The cultivars that in previous years had
demonstrated resistance became susceptible in 2009. Thus resistance and
moderate resistance in 2007 in cvs Bermet, Sharora and Ulugbek 600 became
highly susceptible (IT 100S). Cvs Oktyabrina, Arap, Almaly, Kupava,
Knyazhna and Umanka that were previously immune became susceptible in
2009 (30-40S). New wheat cvs Tungysh, Mereke 70 and Yrym demonstrated a
high level of resistance to yellow rust (IT R-MR). From the F 4-F 5 hybrid
populations, 35 new sources of resistance to yellow rust with infection type 5R-
15MR were identified. All new sources of resistance were included in the
programme of crosses for improving yellow rust resistance.
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Conclusions
The changes of reaction of wheat genotypes (differentials, isogenic lines and
cultivars) to P. striiformis f.sp. tritici indicates changes in pathogen race
composition.
The results of field evaluation of wheat isogenic lines and yellow rust
differentials in Almalybak (Almaty oblast) indicated that the most effective
resistant sources against stripe rust in this region are those of genes Yr5, Yr10,
Yr15 and Yr24, with 0-R infection types. In comparison with 2006 and 2007,
most carriers of yellow rust resistance genes were more susceptible. Virulences
to resistance genes Yr1, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17 and Yr18 have occurred in
the region. The predominant pathotypes in the population of P. striiformis f.sp.
tritici are the races virulent to these genes.
The study of the inheritance of resistance is very important for improving
stripe rust resistance. Genetic analysis was done to determine inheritance of
yellow rust resistance of recombinant inbred lines Almaly × Avocet S. It was